Heat Loss Form Factor & architectural education cc @ElrondBurrell @ecominimalnick

As an architect, Passive House (Passivhaus) designer/consultant and educator (I’m a part-time lecturer at IT Sligo); we are at a critical phase in architectural education as regards aesthetics and energy performance.

A significant factor that contributes to energy loss is what is known as the ‘Heat Loss Form Factor’. The principle is that a home’s type and shape can be collectively described as its ‘Form Factor’, a characteristic that can be defined numerically. The lower the Heat Loss Form Factor, the better.

“A mid-terrace house, for example, has a lower proportion of external wall and therefore a smaller heat loss area than a detached house of the same habitable floor area, and its energy consumption will be lower for that reason alone”: The Challenge of Shape and Form, NHBC Foundation. October 2016

Elrond Burrell has written an excellent post HERE on the Heat Loss Form Factor and I’m not going to go through all the details but the basic mathematics behind it is shown below (The Challenge of Shape and Form, NHBC Foundation. October 2016):

The way to understand the relationship better (as explained in The Challenge of Shape and Form, NHBC Foundation. October 2016) is to ‘unfold’ the building, and with a similar floor area you can see below that a mid-level apartment is more thermally efficient than a detached house:

The above document goes on to compare difference heat loss form factors for different dwelling types where you can see the thermal performance correlated against its Heat Loss Form Factor:

The theory, therefore, is that a ‘complex’ plan where the surface area increases in relation to its floor area will result in an increase in in ‘space heating energy demand’.

The problem, therefore, is that it appears that current architectural education extols complexity over simplicity:

Image from ArchitecturalDigest.com – Heydar Aliyev Centre in Baku, Azerbaijan by Zaha Hadid

Nick Grant explains this well in the slide below where too much design freedom may not be such a great thing – “Does anyone say that a bird is too functional?”

This brings me neatly to an Architecture project that was in a crit last year where the concept was to rather than set the building looking at a gorge, it was set over the gorge (similar to Fallingwater, nice!). My crude sketch shows something along what was intended where the axis of the building is aligned with the gorge and a glass floor allows you to see down into the gorge:

The problem arose that in order to add more accommodation, rather than keeping the single powerful form (first design) that would have a better Heat Loss Form Factor, an additional element was added as below) – this resulted in a much poorer Heat Loss Form Factor and energy performance:

This is a great example where if the original design was kept:

1. Simplifying the design gives a more power architectural form and experience

2. The resulting ‘simpler’ building is thermally more efficient

What’s critical to understand about the principle of the heat loss form factor is that a simpler form (in order to meet the same energy demands) will require either:

• Less thickness of insulation
• Not as high a conductivity
• Use of a more sustainable product such as Sheeps wool as opposed to Carbon intense PIR

And this finally, drum roll please – saves money in the construction and saves the planet!

Comments as always welcome…

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